The most important ingredient in beer, in the actual creation of the beverage, isn’t hops or malt: it’s yeast, the single-celled fungus that also gives us bread. The yeast eats sugars and farts out both carbon dioxide (to make the beer fizzy) and alcohol (we all know what this does, right?). And it turns out, the yeast is also responsible for that special sweet, almost fruity scent of beer. But why?